Due to a recently grown sense of responsibility for the environment and current and prospective emission regulations, it is an object of engine manufacturers to reduce the amount of air pollutants generated by internal combustion engines. Those air pollutants may include particulate matter (PM), nitrogen oxides (NOx), and sulphur components.
Engine manufacturers have developed various approaches to reduce generation and exhaust of air pollutants. A well known technique to reduce generation of NOx is EGR. EGR may be performed by re-circulating a portion of the exhaust gas to the combustion process. Thereby, the temperature within the combustion chamber may be lowered and, thus, the generation of NOx may be reduced. To guide the exhaust gas to the charge air system, EGR lines may branch off at different positions in the exhaust gas system of an internal combustion engine.
For example, a so-called high pressure EGR may have its inlet arranged upstream of an exhaust gas turbine. The terminology “high pressure” is derived from the fact that the extracted exhaust gas has a pressure that is higher than the ambient pressure. The outlet of the EGR line may open into the charge air system of the internal combustion engine, for example, into the charge air manifold or upstream of the charge air manifold and downstream of a charge air cooler.
WO2011/066871 A1 discloses an exemplary embodiment of a high pressure EGR line. The EGR line is interconnected between an exhaust gas line and an air inlet. A high temperature (HT) cooler, an exhaust gas compressor, and a low temperature (LT) cooler are arranged within the EGR line. The extracted exhaust gas may subsequently be cooled in the HT cooler, pressurized in the exhaust gas compressor, and be further cooled in the LT cooler.
Cooling below or within the range of a dew point of an evaporated liquid within the extracted exhaust gas, for example, within a “high pressure” or a “low pressure” EGR line, may result in condensation of that liquid around condensation nuclei. Those condensation nuclei may be PM or a cooling surface of an exhaust gas cooler. As LT cooler typically include a condensation starting region where said dew point may be reached, that condensation starting region may be particularly affected. For example, formation of deposits containing PM and sulphuric acid may deposit on the cooling surface and may subsequently grow during operation. Those deposits (also referred to as fouling) may result in various negative effects on the EGR system and the engine such as an increased pressure drop across the LT cooler, a decreased cooling efficiency of the LT cooler, and/or a corroding cooling surface due to aggressive sulphuric acid.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.